1. Field of Invention
The present invention relates to an image processing apparatus, method and program which perform prescribed color-related processing on a color image.
2. Description of Related Art
Various methods for expressing color image data are available. For example, in a method using the RGB color space, the color of each pixel constituting image data is represented by luminance information of the three primary colors of red, green, and blue. In another method, the color of each pixel is represented by the ink primary colors of cyan (C), magenta (M), yellow (Y), and black (K). In such color representation methods that are generally device-dependent, colors having the same RGB values are seen as different colors according to the human visual sense depending on the color coordinates of primary colors used, the white point definition, etc. For example, the standard known as adobeRGB has a wider color range than the standard known as sRGB, which was established to serve as an HDTV color standard, and therefore colors having the same RGB values are seen differently according to these two standards. Similarly, a color according to the print color samples of JapanColor and a color according to those of SWOP, which is a U.S. print standard, are seen (appear) differently even if they have the same CMYK values.
In recent years, to eliminate the above-described non-coincidence in color representation, image data formats have been developed in which image data contains information (color space identification information) indicating a color space that is used for expressing the image data. Specifically, a data format called “ICC (International Color Consortium) profile” that includes color information is known.
However, the present situation is such that much of the conventional image data that are generated and used in many devices do not contain such color space identification information. For this reason, a method of using a pre-assumed color space and a method of causing a user to input color space identification information of image data are widely used when it is necessary to identify a color space to, for example, change color spaces. However, in the method of using a pre-assumed color space, a desired processing result is not obtained if a color space actually employed is different from the assumed one.
The method of causing a user to input color space identification information has a problem in that it is less convenient because the user needs to check a color space.
Further, even if image data contains color space identification information, there is a possibility that it is in error. Thus, there is a need for a method for checking the legitimacy of color space identification information contained in image data.